US20030231597A1

Movatterモバイル変換

Info

Publication number: US20030231597A1
Application number: US10/443,424
Authority: US
Inventors: Lance Hester; Qicai Shi; Jian Huang; Edgar Callaway
Original assignee: Individual
Current assignee: Arris Enterprises LLC
Priority date: 2002-05-23
Filing date: 2003-05-22
Publication date: 2003-12-18
Also published as: US7440462B2

Abstract

Mediation devices in an asynchronous network of low power consumption communication devices are leveraged through the use of new protocols (2500) that analyze relevant QoS parameters (2520) in order to provide a better than best effort service in the network. These protocols invoke adaptive quality of service (QoS) mechanisms to capitalize on the strength and flexibility provided to the network by the presence of one or more MDs, as described above. Expanded functionality of the MD includes control information messaging and service differentiation for the purpose of improving QoS of the network.

Description

RIGHT OF PRIORITY

This application claims priority to and benefit of earlier filing date of U.S. Provisional Application No. 60/383,454, filed May 23, 2002 and being further identified by attorney docket number CML0363J, the content of which is incorporated herein by reference.[0001]

CROSS REFERENCE TO RELATED APPLICATIONS

This application is related to the following copending applications entitled “Beacon Assisted Hybrid Asynchronous Wireless Communications Protocol” (Docket No. CM03694J), “System and Method for Asynchronous Communications Employing Direct and Indirect Access Protocols” (Docket No. CM03695J), “A Multiple Access Protocol and Structure for Communication Devices in an Asynchronous Network” (Docket No. CM03526J), and are herein incorporated by reference.[0002]

FIELD OF THE INVENTION

The present invention relates generally to communication networks and more specifically to quality of service (QoS) concerns in asynchronous communication networks.[0003]

BACKGROUND OF THE INVENTION

In communication networks, asynchronous transmission of information is often the technique used when communicating information between one or more communication devices within a communication network. Asynchronous transmission is often used when low power devices make up the network. These low power devices can use a low communication duty cycle frame structure in order to minimize the amount of power used while not actively communicating with other network devices, but the use of a low communication duty cycle frame structure often implies that device availability is reduced. In wireless communication networks, a fundamental challenge is maintaining high availability communications while using low power wireless communication devices.[0004]

The neuRFon™ device by Motorola is an example of a low power, low cost, small size, and simple wireless device. The neuRFon™ device network is a zero-configuring, self-organizing, asynchronous network containing multiple neuRFon™ devices. For this network, power consumption and cost are two major concerns.[0005]

To lower the power consumption, the average communication duty cycle of all the devices in the described network has to be decreased to a minimum. The average communication duty cycle refers to the fraction of time that the wireless device is able to send and receive messages. For the described asynchronous network, the average communication duty cycle may be set so low that the infrequent communications between a transmitter and a destined receiver become a problem. For example, device A may attempt to contact device B, but device B may be not be able to receive messages due to its low average communication duty cycle. This will prevent device A from establishing contact.[0006]

A representative low average communication duty cycle frame structure, in which the above problem is illustrated, is shown in FIG. 1. Using this frame structure, a low average communication duty cycle device uses 1 ms to warm up, 1 ms to transmit and receive messages from other devices in its group, and is asleep for the remaining 998 ms of the 1 second cycle. This gives a communication duty cycle of about 0.1%, which is very power efficient.[0007]

The problem with this approach is illustrated in FIG. 2. FIG. 2 shows a small network comprising several low power, low average communication duty cycle devices, where each device is represented as a small dot. Referring again to FIG. 2, device A tries to talk to device B. If the low average communication duty cycle frame structure in FIG. 1 is assumed, both A and B devices are able to communicate only 0.1% of the time. If we further make the reasonable assumption that device A and device B don't each have access to the other's time schedule, the probability of device A to establish communication with device B is approximately 0.1%, which is too small for most applications.[0008]

Another concern in such networks is packet loss. Network congestion often contributes to this problem, particularly in wireless networks. The behavior of wireless links existing between communication nodes or devices can be highly unpredictable due to the occurrence of fading, interference, and even deployment of the devices in unknown terrains. In such networks, there is an expectation that packet loss will occur as the traffic load on the network increases due to the greater exchange of data packets. This can have a substantial and adverse impact on service quality of the network and can cause the network to only provide best effort support in which there is no guarantee a message will indeed be sent and received.[0009]

BRIEF DESCRIPTION OF THE DRAWINGS

The novel features believed characteristic of the invention are set forth in the claims. The invention itself, however, as well as a preferred mode of use, and further objects and advantages thereof, will best be understood by reference to the following detailed description of an illustrative embodiment when read in conjunction with the accompanying drawings, wherein:[0010]

FIG. 1 is a low communication duty cycle frame structure, according to the prior art.[0011]

FIG. 2 is a low power communication device network, according to the prior art.[0012]

FIG. 3 is a block diagram illustrating the internal functionality of a low power device, in accordance with certain embodiments of the present invention.[0013]

FIG. 4 is a network containing multiple low power devices and a single dedicated Mediation Device (MD), in accordance with certain embodiments of the present invention.[0014]

FIG. 5 illustrates the internal functionality of a dedicated MD, in accordance with certain embodiments of the present invention.[0015]

FIG. 6 is a low communication duty cycle frame structure for a low power device, in accordance with certain embodiments of the present invention.[0016]

FIG. 7 is a high communication duty cycle frame structure for a dedicated MD, in accordance with certain embodiments of the present invention.[0017]

FIG. 8 is a flowchart for dedicated MD operation, in accordance with certain embodiments of the present invention.[0018]

FIG. 9 is a timing diagram for communication between two low power devices and a dedicated MD when a query occurs later than the communication request, in accordance with certain embodiments of the present invention.[0019]

FIG. 10 is a flowchart for communication between two low power devices and a dedicated MD when the query occurs later than the communication request, in accordance with certain embodiments of the present invention.[0020]

FIG. 11 is a timing diagram for communication between two low power devices and a dedicated MD when the query occurs earlier than the communication request, in accordance with certain embodiments of the present invention.[0021]

FIG. 12 is a flowchart for communication between two low power devices and a dedicated MD when the query occurs earlier than the communication request, in accordance with certain embodiments of the present invention.[0022]

FIG. 13 is a network containing multiple low power devices and an additional low power device functioning as a MD, in accordance with certain embodiments of the present invention.[0023]

FIG. 14 is the internal functionality of a low power device operable as a MD, in accordance with certain embodiments of the present invention.[0024]

FIG. 15 illustrates a low communication duty cycle frame structure for a low power device functioning as a MD, in accordance with certain embodiments of the present invention.[0025]

FIG. 16 is a timing diagram for communication between two low power devices and a third low power device acting as MD when the query occurs later than the communication request, in accordance with certain embodiments of the present invention.[0026]

FIG. 17 is a flowchart of the communication between two low power devices and a third low power device acting as MD when the query occurs later than the communication request, in accordance with certain embodiments of the present invention.[0027]

FIG. 18 is a timing diagram for communication between two low power devices and a third low power device acting as MD when the query occurs earlier than the communication request, in accordance with certain embodiments of the present invention.[0028]

FIG. 19 is a flowchart for the communication between two low power devices and a third low power device acting as MD when the query occurs earlier than the communication request, in accordance with certain embodiments of the present invention.[0029]

FIG. 20 is a timing diagram illustrating a collision between two low power devices acting as MD when a collision avoidance strategy is not used, in accordance with certain embodiments of the present invention.[0030]

FIG. 21 is a timing diagram illustrating the collision avoidance strategy between two low power devices acting as MD, in accordance with certain embodiments of the present invention.[0031]

FIG. 22 is the collision avoidance strategy flowchart, in accordance with certain embodiments of the present invention.[0032]

FIG. 23 is a timing diagram for a multiple access scheme for a small network of low power devices, wherein each device is operable as a MD, in accordance with certain embodiments of the present invention.[0033]

FIG. 24 is a low communication duty cycle frame structure for a multiple access scheme for a small network of low power devices, wherein each device is operable as a MD, in accordance with certain embodiments of the present invention.[0034]

FIG. 25 is a flowchart illustrating an approach for achieving improved QoS performance in an asynchronous network, in accordance with certain embodiments of the present invention.[0035]

FIG. 26 illustrates an exemplary header packet containing QoS parameters useful for achieving improved performance in an asynchronous network, in accordance with certain embodiments of the present invention.[0036]

FIG. 27 illustrates an exemplary data packet containing QoS parameters useful for achieving improved performance in an asynchronous network, in accordance with certain embodiments of the present invention.[0037]

DESCRIPTION OF THE INVENTION

While this invention is susceptible of embodiment in many different forms, there is shown in the drawings and will herein be described in detail specific embodiments, with the understanding that the present disclosure is to be considered as an example of the principles of the invention and not intended to limit the invention to the specific embodiments shown and described. In the description below, like reference numerals are used to describe the same, similar or corresponding parts in the several views of the drawing.[0038]

In order to keep the power consumption at a minimum, and yet still achieve reliable communication, a mediation device (MD) is introduced. The MD acts as a mediator between communication devices within the network, and is capable of recording and playing back message related information. This is most useful when two communication devices are unable to establish contact. More than one MD may also be used in a large network, where each MD mediates for a group of low-power, low communication duty cycle communication devices. The MD has a relatively high communication duty cycle as compared to the low-power communication devices in the group and is thus able to store and forward messages between two or more low power communication devices in the asynchronous network. Note that the MD functionality may actually be a feature of the low power communication devices in the group. In this case, each low power communication device may be operable as a MD within the asynchronous network, with a low power communication device of the network being randomly chosen to temporarily operate as a MD of the group. This allows the overall network to remain a low power, low cost asynchronous network and each low power wireless device to remain a low communication duty cycle device, except when serving as a MD. Since a low power wireless device is a MD only occasionally, the average communication duty cycle of each low power wireless device can remain low. Distributing MD functionality across all the communication devices in the network also allows the communication devices to use energy mining in order to increase the average communication duty cycle of the communication devices in the network.[0040]

During normal asynchronous network operation, each communication device except those serving as MD has a low communication duty cycle frame structure. The communication duty cycle of the MD may be adapted to the design parameters of the network, so that changing the parameters of the MD has an impact on the availability of each communication device within communication range of the MD.[0041]

The present invention discloses a method and structure for a low power consumption protocol for low power wireless devices attached to an asynchronous network. Referring to FIG. 4, a simplified representation of a[0042]

network

400 containing aplethora440 of lowpower communication devices410 and adedicated MD430 is shown, according to a first embodiment of the present invention. Each of the lowpower communication devices410 ofnetwork400 has a low communication duty cycle and must therefore rely upondedicated MD430 for reliable communication.Dedicated MD430 has a high communication duty cycle in comparison to the non-MDlow power devices410, and can store messages destined for any of lowpower wireless devices410 within thegroup440.

Referring now to FIG. 6, a representative low communication duty[0044]

cycle frame structure

600 characteristic of the low power, low communication duty cycle devices of the network is shown. Asingle frame670 of low communication dutycycle frame structure600 contains a warm-up block610, acommunication block620, and asleep block650. Warm-upblock610 occurs first chronologically, and is a very small percentage of the overall frame duration. Warm-upblock610 is followed bycommunication block620.Communication block620 is also a small percentage of the overall frame duration. Aftercommunication block620 ends,sleep block650 begins.Sleep block650 is a relatively high percentage of the overall frame duration in order to preserve the low communication duty-cycle characteristic of the device. Exemplary values are Ims for warm-

up block

610, 1 ms forcommunication block620, and 998 ms forsleep block650, although these values can be changed significantly without departing from the invention. At the end offrame670, the three-

block cycle

610,620,650 is repeated for the next frame. This block order is preserved for all frames in the low communication dutycycle frame structure400. In the preferred first embodiment,communication block620 may be further subdivided into a transmit period and a receive period, although it will be clear to one of skill in the art that the communication devices-in the network can have multiple transmit and receive periods withincommunication block620. Under normal operation of the first preferred embodiment, the receive period occurs first, followed by a transmit period of equal duration. Under certain situations, such as synchronization between communication devices, the transmit period may occur before the receive period.

Referring now to FIG. 7, a representative high communication duty[0045]

cycle frame structure

Referring now to FIG. 8, a flow diagram[0046]800 for applying the dedicated MD to communication between a communication device A, and a communication device B, according to the first preferred embodiment, is shown. Inblock820, device A attempts to communicate with device B. If B is reachable, thendecision block830 evaluates to No and device A establishes communications with device B as shown inblock860. Device A and device B then return to normal operation, as shown intermination block870. If the answer indecision block830 is Yes, then device B is not available, and device A communicates contact information with the dedicated MD as shown inblock840. Inblock850, dedicated MD replays the contact information for device B when device B is able to communicate. Device B uses this contact information to synchronize communications with device A. Device A is now able to communicate with device B, as shown inblock860. After device A communicates with device B, both devices return to normal operation, as shown inblock870. Note that device A can fail to reach device B when device B is in sleep mode, in transmit mode, out of range, or other similar reasons.

Referring now to FIG. 9, a more detailed timing diagram is shown for the case described in FIG. 8, according to the first embodiment. As in FIG. 8,[0047]

device A

910 attempts to communicate withdevice B920, but is not successful, sodedicated MD930 is used to mediate betweendevice A910 anddevice B920 untildevice B920 is able to communicate.Device A910 is a low duty cycle device with a communication period containing a receiveslot965 and a transmitslot970.Device B920 is also a low duty cycle device with a communication period containing receiveslot985 and transmitslot990.Dedicated MD930 contains a communication period that is much longer than either communication period ofdevice A910 ordevice B920. The communication period ofdedicated MD930 similarly contains a receiveperiod975 and a transmitperiod980. Referring also to FIG. 10, the flowchart for the timing diagram of FIG. 9 is shown. The flow inblock1020 of FIG. 10, as well as the timing diagram of FIG. 9, assume thatdevice A910 has not been successful in communicating directly withdevice B920. So, there is a need fordevice A910 to use thededicated MD930 to store a communication request withdevice B920. As shown inblock1030,device A910 sends acommunication request935 todedicated MD930 during the transmitslot970 of the communication period ofdevice A910.Communication request935 is received bydedicated MD930 during the receiveslot975 of the communication period ofdedicated MD930. Also during the receiveperiod975,device B920 enters its communication period. Upon waking,device B920 sends aquery940 using transmitslot990 todedicated MD930 to check for messages. Note that bothdevice A910 anddevice B920 are able to communicate withdedicated MD930 during a single receiveslot975. The duration of receiveslot975 and transmitslot980 ofdedicated MD930 should be chosen large enough thatdedicated MD930 is able to receive both communication request and query messages. SinceMD930 receivedcommunication request935 fromdevice A910 prior to thequery940 fromdevice B920, during thetransmission slot980 of the communication period ofdedicated MD930

dedicated MD

930 first sends anacknowledgement945 todevice A910 during receiveslot965 in the next communication period ofdevice A910, as indicated inblock1040.Dedicated MD930 then sends areplay message950 todevice B920 during the same transmitslot980 of the communication period ofdedicated MD930, as indicated inblock1050. In the first preferred embodiment, the communication period of each communication device in the network occurs with a fixed period, so thatdedicated MD930 is able to sync withdevice B920 withoutdevice B920 sending synchronization information. However, other implementations of the second embodiment could require each communication device in the network to transmit explicit synchronization information todedicated MD930, so that the query message would contain synchronization information.Device B920 now has enough information to enable communications withdevice A910 without the use ofdedicated MD930. In order to synchronize with device A, device B uses timing information provided in thecommunication request935 ofdevice A910, and swaps communication slots so that the transmitslot990 precedes the receiveslot985 ofdevice B920. As shown inblock1060,device B920 then sends anacknowledgement955 to device A during the receiveslot965 of the communication period of device A. As shown inblock1070,device A910 is now able to communicate amessage960 todevice B920 during the transmitslot970 ofdevice A910 and the receiveslot985 ofdevice B920. Once the communication betweendevice A910 anddevice B920 is complete,device A910 anddevice B920 return to normal operation, as shown inblock1080.

The discussion above referring to FIG. 9 and FIG. 10, illustrated the sequence of communication operations and timing flow for the case in which the query from[0048]

device B

920 is later than the communication request fromdevice A910. It is also possible for the query ofdevice B920 to precede the communication request ofdevice A910. This scenario is illustrated in the timing diagram of FIG. 11, and the flowchart of FIG. 12. The sequence of operations shown in FIG. 12 is identical to those in FIG. 9, except thatdevice A910 first attempts to communicate acommunication request1150 with dedicatedMD930 during a time that dedicatedMD930 is unavailable, as inblock1230. Since thededicated MD930 is not available,device A910 has to wait until a communication period in whichdedicated MD930 has an active receiveperiod975. This delay means thatdevice B920 sendsquery940 to the receiveslot975 ofdedicated MD930 prior to thecommunication request935 ofdevice A910, as inblock1240. It is important to note that since both the transmitslot975 and receiveslot980 ofdedicated MD930 are as long as two transmit periods ofdevice A910 ordevice B920, during the transmit slot ofdedicated MD930, dedicated MD is able to replaymessage950 todevice B920 and acknowledge945

device A

910. This allows the handshake betweendevice A910 anddevice B920 to proceed as in block1060-1080. So, the ordering of thecommunication request935 and thequery940 within a single receiveslot975 and the ordering ofreplay950 andacknowledgement945 within a single transmitslot980 ofdedicated MD930 does not affect establishment of communications betweendevice A910 anddevice B920.

Instead of using[0049]

dedicated MD

There are several approaches that may be used to select the next MD. The MD could be selected at random when the low power communications device acting as MD is not able to act as MD any longer. If each MD uses a randomly generated initial phase offset t[0050]0, then the distribution of MD functionality across the low power communication devices within the network should be uniform. This selection process will prevent collisions between two low power communications devices attempting to concurrently act as MD, but it requires coordination amongst the low power communication devices within the network. A second approach, and the one used in the second preferred embodiment, is to let each low power wireless device randomly determine when it will act as MD. In the case of two low power communication devices acting as MD, a collision avoidance strategy will be used to ensure only one MD is within communication range of a low power communication device.

Referring now to FIG. 15, a representative low communication duty[0052]

cycle frame structure

1500 of lowpower communication device1400 functioning as MD is shown. Low communication dutycycle frame structure1500 contains several cycles of operation in which each cycle contains a plethora of frames that are repeated multiple times. A first frame of the plethora of frames of low communication dutycycle frame structure1500 contains a randomdelay t0 block1535, a warm-up block1505, and acommunication block1510. The random delay hasduration t01535, where t0 is between 0 and the duration of a single transmit or receive period. This delay randomizes the start time of the communication devices in the network, so that the probability of multiple devices to function as MD concurrently is reduced. Warm-up block1505 occurs next chronologically, and is a very small percentage of the overall frame duration. Warm-up block1505 is followed bycommunication block1510. Note thatcommunication block1510 and warm-up block1505 directly follow therandom delay t01535. However, it is also feasible forcommunication block1510 and warm-up block1505 to be delayed a random amount during the start of the next cycle of operation. In other words, the timing ofcommunication block1510 within the sequence of cycles is not constrained to be periodic.Communication block1510 is a large percentage of the overall frame duration, and further comprises a receiveslot1525 and atransmission slot1530. In the second preferred embodiment, the one receiveslot1525 precedes the one transmitslot1530, although the order could be switched. Also, one of ordinary skill in the art will recognize thatcommunication block1510 could contain several transmit and receive slots in various arrangements. Also, although transmitslot1530 occurs directly before or directly after receiveslot1525, the hardware contained in the transmitter and receiver will require some time to switch between the transmit and receive modes. The duration of the switching time can be dependent on the switching speed of the hardware in the communication devices, or it could be determined by a user specified parameter in the communication device processor.

After[0053]

communication block

1510 ends, a second frame having a duration roughly one half ofcommunication block1510 begins. Second frame contains one sleep block1515. Sleep block1515 is a very high percentage of the overall frame duration. At the end of the second frame the lowpower communication device1400 resumes low communication duty cycle operation starting with a third frame of the plethora of frames. The low communication dutycycle frame structure1500 is shown in FIG. 6. Low communication duty cycle operation occurs for several frames of the plethora of frames of low communication dutycycle frame structure1500. The duration of the first cycle of low communication dutycycle frame structure1500 is a random number that is generated by thecommunication device1400 at the start of thedelay block1535.

At the conclusion of the first cycle, the entire framing sequence just described is repeated until low[0054]

power communication device

1400 stops functioning as MD. The decision to stop functioning as MD is made solely by the lowpower communication device1400 in the second preferred embodiment, although it is also possible to coordinate the role of MD among several low power communication devices. Note that lowpower communication device1400 contains the ability to generate and store random or pseudo-random numbers. These numbers could be generated byMD processor1430, and stored inMD memory1460.

Referring now to FIG. 16, a detailed timing diagram for a[0055]

device A

[0056]

Device B

1620 now has enough information to enable communications withdevice A1610 without the use ofdevice C1630. In order to synchronize with device A, device B uses timing information provided in thecommunication request1635 ofdevice A1610, and swaps communication slots so that the transmitslot1690 precedes the receiveslot1685 ofdevice B1620. As shown inblock1780,device B1620 then sends anacknowledgement1655 to device A during the receiveslot1665 of the communication period of device A. As shown inblock1790,device A1610 is now able to communicate amessage1660 todevice B1620 during the transmitslot1670 ofdevice A1610 and the receiveslot1685 ofdevice B1620. Once the communication betweendevice A1610 anddevice B1620 is complete,device A1610 sleeps for a randomly generated duration ta1661 anddevice B1620 sleeps for a randomly generatedduration tb1662.Device A1610 anddevice B1620 then return to normal operation, as shown inblock1795.

The discussion above referring to FIG. 16 and FIG. 17, illustrated the sequence of communication operations and timing flow for the case in which the query from[0057]

device B

1620 is later than the communication request fromdevice A1610, according to the second embodiment. It is also possible for the query ofdevice B1620 to precede the communication request ofdevice A1610. This scenario is illustrated in the timing diagram of FIG. 18, and the flowchart of FIG. 19. The sequence of operations shown in FIG. 18 is similar to those in FIG. 11, except thatdevice C1630 is a low power communication device functioning as a MD, rather than the dedicatedMD930 shown in FIG. 11. Since thedevice C1630 is not available, thefirst communication request1850 ofdevice A1610 is not received as shown inblock1930, anddevice A1610 has to wait until a communication period in whichdevice C1630 has an active receiveperiod1675, as shown inblock1940. This delay means thatdevice B1620 sendsquery1640 to the receiveslot1675 ofdevice C1630 prior to thecommunication request1635 ofdevice A1610, as inblock1950. It is important to note that since both the transmitslot1675 and receiveslot1680 ofdevice C1630 are as long as two transmit periods ofdevice A1610 ordevice B1620, during the transmit slot ofdevice C1630, device C is able to replaymessage1650 todevice B1620 and acknowledge1645

device A

1610. This allows the handshake betweendevice A1610 anddevice B1620 to proceed as in block1985-1990. So, the ordering of thecommunication request1635 and thequery1640 within a single receiveslot1675 and the ordering ofreplay1650 andacknowledgement1645 within a single transmitslot1680 ofdevice C1630 does not affect establishment of communications betweendevice A1610 anddevice B1620. Once the communication betweendevice A1610 anddevice B1620 is complete,device A1610 sleeps for a randomly generated duration ta1661 anddevice B1620 sleeps for a randomly generatedduration tb1662.

For the second embodiment of the present invention, it is possible for two communication devices within the network to independently decide to function as MD's at the same time. If this occurs, then it is possible that the transmit periods of the two devices of the two devices overlap and a collision results. This situation is illustrated in FIG. 20.[0058]

Device A

2010 first starts to function as MD. A short time later, a second device B starts to function as MD. Whentransmission slot2040 ofdevice A2010 overlapstransmission slot2060 ofdevice B2020, the two transmitters interfere and communications capability is degraded. Note that the issue of collision is only a problem when the transmitters in the communication devices within the network occupy overlapping frequency bands and the communicated bit rate/bandwidth is high. If the transmitter data is modulated using a spreading waveform, then the communication devices could occupy the same frequency band and collisions could be less of an issue. According to the preferred second embodiment, each of the communication devices are single-channel devices using the same transmission frequency, so that the collision issue must be addressed.

Referring now to the timing diagram of FIG. 21, and the flowchart of FIG. 22, a collision avoidance strategy is described according to the second embodiment of the present invention.[0059]

Device A

2105 is randomly selected as MD prior todevice B2115. At the start of the MD mode ofdevice A2105, device A transmits announcement message2120 (block2210) in a very shortduration transmission slot2122, and then switches to receiveslot2125 of communication period2160 (block2220).Device B2115 is then randomly selected as MD, anddevice B2115 sends out announcement message2120 (block2230) in a very shortduration transmission slot2140 prior to switching to receiveslot2145 ofcommunication period2160. Device A receives theannouncement message2120 of device B2115 (block2240) during receiveslot2125, and generatesalarm message2130 during it's next transmit period2135 (block2250).Device B2115 receives thisalarm message2130 during receiveperiod2145, and immediately stops acting as MD (block2260).Device B2115 then sleeps a random amount of time t2 to prevent future collisions and resumes operation as a normal low power communication device (block2270). Instead of sleeping for t2 seconds,device B2115 could wait until the end of the MD communication period ofdevice A2105. At this time,device B2115 functions as a MD, sincedevice A2105 is not incommunication period2160.

According to the second preferred embodiment, the random initial offset to[0060]1535 is between 0 and 1sleep period1545, the amount of delay ta1661 andtb1662 are between 0 and 1 sleep period1515, and thecycle time t11560 follows the inequality, 0.5T<t1<1.5T, where T is the average frequency of the communication period of a communication device acting as MD.

The second embodiment of the present invention presents a protocol and structure for a network of low power communication devices to improve the reliability of inter-device communication through the use of a Mediation Device (MD). One issue with this approach is the reliability when the number of communication devices in the network is small. As an example, if the network contains only five communication devices, and the MD communication cycle of each is 1000 seconds (t[0061]1), then the average latency will be roughly 200 seconds. One way to reduce the latency is to constrain all nodes to communicate within a specified time window.

Referring to FIG. 23, a multiple access scheme in which[0062]

N communication devices

2310 are in the network, according to a third embodiment of the present invention. Each communication device of the N communication devices is constrained to receive and transmit information within awindow2320 of duration Tw seconds. Duration Tw is selected from the size of the network as determined by the number of communication devices in the network.

For example, for a network with five communication devices operating within a t[0063]1 period of 1000 seconds, the average latency is 200 seconds. If the communication cycle t1 is reduced to 300 seconds, the average latency is reduced by a factor of three. If the duration Tw ofwindow2320 is smaller than the communication period of the communication device, the duration of the communication period must be reduced to fit withinwindow2320. Reducing the duration of the communication period increases the likelihood of communication devices moving out of communication range without the knowledge of communication device acting as MD. Also, new communication devices entering the network will not be recognized unless their communication period lies within thewindow2320.

One solution to this is illustrated in FIG. 24, according to the third embodiment of the present invention. The timing diagram[0064]2400 of FIG. 24 shows a communication device which has a shortened communication period so that the communication device is able to communicate withinwindow2420. In order to check for new communication devices, or recognize the loss of existing communication devices, along communication period2410 is occasionally used when the communication device is acting as MD. Thislong communication period2410 is followed by the low powercommunication duty cycle2430 structure of FIG. 6, and additional shortMD communication periods2420. With the exception of thelong communication periods2410, the communication device has essentially the same low communication duty cycle frame structure illustrated in FIG. 15 of the second embodiment.

As an example of the third embodiment, a[0065]

long communication period

2410 of 2 seconds, ashort communication period2420 of 200 ms, and the normal low communication duty cycle mode with a communication period of 2 ms is used. The frequency of thelong communication period2410 is 1500 seconds, the frequency of the short communication period is 300 seconds, and the frequency of the normal communication period is 1 second. This leads to a duty cycle of about 0.4%.

It is noted that the communication device described herein may be a NeuRFon® device or any suitable communication device having similar operating characteristics.[0066]

The use of mediation devices in an asynchronous network can be further leveraged through the use of new protocols to provide a better than best effort service in the network. These protocols invoke adaptive quality of service (QoS) mechanisms to capitalize on the strength and flexibility provided to the network by the presence of one or more MDs, as described above. Expanded functionality of the MD includes control information messaging and service differentiation for the purpose of improving global QoS of the network. The improved QoS protocols are applicable to both dedicated and distributed mode MDs and are implemented and controlled by the processing and control blocks of the MD (referred to by[0067]

reference numerals

340,350,540,550 and discussed above). As previously noted, the processing and control functions may reside in the same or separate parts of the MD.

In accordance with certain embodiments of the present invention, a method for providing improved quality of service (QoS) control in an asynchronous network having a mediation device and a plurality of communication devices is envisioned. Quality of service (QoS) parameters, relevant to a communication request received from a sender communication device to send a communication to a target communication device, are analyzed by a MD. Analysis by the MD allows it to make a determination about whether the service request can be serviced or not. If it is determined that the service request can be serviced, i.e. is supportable by a target device, than the MD sends the communication message on to its intended recipient. A decision to honor the communication request may optionally result in an acknowledgement message being communicated by the MD to the sender communication device, the target communication device or both. Alternately, a decision that the communication request cannot be serviced, may result in the MD sending a service message indicating the same to the sender communication device.[0068]

As will become clear, the decision about whether the communication request can be serviced may be based upon one or more types of QoS parameters, which can include sender QoS (SQoS) parameters relevant to certain communication criteria of the sending communication device, target QoS (TQoS) parameters relevant to the ability of the target communication device to receive the communication intended for it, mediation device QoS (MDQoS) parameters descriptive of the ability of the MD itself to service the communication request, and network QoS (NQoS) parameters indicative of health of the network and thus its ability to support the communication request.[0069]

Referring now to the[0070]

flowchart

2500 of FIG. 25, atBlock2510, the MD receives packets from non-MD device(s) submitting their communication requests. The communication requests may come in the form of packets, namely a beacon or header packet, such as that illustrated in FIG. 26, and an accompanying data packet, as in FIG. 27.Exemplary beacon packet2600 may include a number of fields, such aspreamble2610, start frame delineator (SFD)2620,destination address2630,source address2640,frame type2650,QoS parameters2660, and cyclic redundancy check (CRC)2670. Theframe type2650 will include information about what type of data, such as data, video, voice, etc., will follow in thepayload field2780 and thus may be important information relating to the communication criteria to provide to the MD. In FIG. 27, adata packet2700 may contain the following fields:preamble2710,SFD2720,destination address2730,source address2740,frame type2650,frame length2760,QoS parameters2770, payload (data)2780, and cyclic redundancy check (CRC)2790.

The QoS fields[0071]2660 and2770 of the beacon and data packets contain information the sender communication device wishes to communicate to the MD concerning communication criteria to be met for the communication of the message (payload) to the target communication device. Such QoS information is referred to as SQoS parameters and may include, by way of example and not limitation, the following: expiration time of the data, packet type (normal, emergency, video, voice, private, public), sender identification (address), sender status, economic (the amount paid for what class of delivery service), the data rate of the sender communication device, method of encoding, the proposed length of the transmission, the message length for fragmentation purposes, the type of power (such as battery) still available to the sender communication device, memory size (may indicate its ability to prevent fragmentation of the message), etc.

Service differentiation may additionally be availed to improve QoS of the network based upon additional SQoS parameters. Based upon fields located in the data packet headers ([0072]2770), the MD can prioritize the order in which packet delivery should occur, thereby allowing the MD to provide different levels of service to communication devices based on predefined data attributes. For example,QoS field2770 may give the expiration time of the data sought to be delivered (2780) so that the MD can provide packets with faster approaching expiration periods a higher delivery priority. Similarly, the QoS field may specify which packets can or cannot be dropped if the buffer of the MD exceeds its capacity. Moreover, authenticating information to allow the MD to authenticate a communication device before adding it may be provided to the MD as well.

The relevant QoS parameters are gathered and analyzed by the MD at[0073]

Block

2520 and are used by the MD to make a determination about how, when, if, etc. the communication request will be serviced atBlock2530. Any problems identified atDecision Block2540 may result in a service message being sent to the sending communication device regarding the problem and possibly providing suggestions on how to proceed. For instance, if it is determined that the target device does not have enough power to be on long enough to receive the transmission, then the MD may send a service message to the sender asking it to cease its transmission attempts. If there is no problem supporting the communication request, then the MD may send an acknowledgement message (such as with a synchronization signal) to one or both of the sending communication device and the target communication device atBlock2560. It will then service the communication request by transmitting the communication to the intended target communication device atBlock2570.

The SQoS parameters have been discussed above and are used by the MD to start the analysis process at[0074]

Block

2520. The MD may also look at other QoS parameters, such as the ability of the MD to support the communication (MDQoS parameters), the ability of the network to support the communication (NQoS parameters), and particularly the ability of the target communication device to receive the message intended for it in accordance with the communication criteria set forth by the sending communication device (TQoS parameters). TQoS parameters may include, by way of example and not limitation, the following: power available to the target (reflects how long it will be “on” and available to receive), ability to deal with the type of data to be transmitted, its ability to support the encoding, ability to sustain communications for the time desired, etc. NQoS parameters reflect the network environment and potentially its ability to deal with the communication request and may include, by way of example and not limitation: interference levels within the neighborhood supported by the MD, the communication demands currently experienced by other communication devices within range. By way of example and not limitation, the MDQoS parameters may include the following: the logical position of the MD within the network with regard to other non-MD communication devices within range, the devices in range of the MD, the current channel traffic such as the number of messages sent in the last hour, for instance, the type of messages being sent, the status of other MDs in range (there may be another MD that can handle a communication if the instant MD is unable to), etc.

It is noted here that the MD need not gather and analyze all of these various types of QoS data. It may be prepared to make a decision concerning the communication request given very little or a lot of parameter information. For instance, the MD may decide to whether to support a communication request based simply on the communication criteria received from the sender and whether the target is on. Obviously, however, the more information that is considered by the MD, the better the QoS of the network. A determination made by the MD based upon SQoS, TQoS, MDQoS, and NQoS will be, in a lot of instances, a better reasoned decision than one based solely upon limited SQoS and TQoS parameters.[0075]

As regards the interference parameter, consider the effect a communication device entering the network in proximity to the MD and having a similar operating frequency would have. If measured interference surpassed a predefined acceptable threshold, the MD could transmit control information to all the regular, non-MD communication devices Within range. Moreover, the communication demand parameter would be useful if a particular communication device, needed to facilitate getting the communication to the target communication device, is experiencing a particularly heavy demand, indicative of a problem (Decision Block[0076]2540). This information may prompt the MD to alert the sending communication device of the problem by sending a service message (Block2550) informing the sender that the communication channel is currently highly error prone and susceptible to a corrupted transmission. The sending device could then make a decision to buffer its data or have the MD buffer the data until the problem has alleviated.

By performing one or more of screening incoming packets, rating the capability of non-MD nodes (such as the target communication device and any intervening nodes between the MD and the target) to carry on successful communications, and measuring the quality of the communication channel through NQoS parameters, the MD provides enhanced QoS assurance for a fully distributed network in a local manner. Because of the MD control information, in the form of various QoS parameters, discussed above, individual communication devices of the network need only know their own capabilities and have knowledge of the channel in their intermediate vicinity. Consequently, the number of unsuccessful transmissions, and, therefore, re-transmissions, may be significantly reduced, resulting in a tremendous savings in battery life of the communication devices and better utilization of limited bandwidth resources in the network. Moreover, the ability to process data packets and develop a packet hierarchy allows the MDs of the network to provide a mechanism for ensuring that some packets will be delivered in a more timely manner through exercise of service differentiation principles and that others discarded if so desired.[0077]

While the invention has been particularly shown and described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the invention. For example, one of ordinary skill in the art will recognize that low power devices may by physically connected or wireless, without departing from the spirit and scope of the invention. In the first, second, and third preferred embodiments, single-channel communication devices are contained in each of the first, second and third preferred embodiments. Also, for each preferred embodiment, the transmit slot and receive slot of a communication device of the plurality of communication devices do not overlap. For all three embodiments, the duty cycle is defined as the fraction of time that the communication device is in either a transmit slot or a receive slot. Also for all three embodiments, the communication device is assumed to be a low communication duty cycle, low power, wireless device, but, again, this need not be the case.[0078]

Moreover, those of ordinary skill in the art will recognize that the present invention has been described in terms of exemplary method embodiments and that these embodiments may be implemented by means of computer-readable media tangibly embodying a program of instructions executable by a computer or programmed processor, as well as hardware equivalent components such as special purpose hardware and/or dedicated processors. Similarly, general purpose computers, microprocessor based computers, micro-controllers, optical computers, analog computers, dedicated processors and/or dedicated hard wired logic may be used to construct alternative equivalent embodiments of the present invention. Such alternatives should be considered equivalents.[0079]

The present invention may accordingly be implemented using one or more programmed processor executing programming instructions that are broadly described above in flow chart form and which can be stored in any suitable electronic storage medium. However, those skilled in the art will appreciate that the processes described above can be implemented in any number of variations and in many suitable programming languages without departing from the present invention. Thus, the process can be described by a set of instructions implementing the processes described and stored on a computer storage medium such as a magnetic disc, optical disc, magneto-optical disc, semiconductor memory, etc. Many such variations and modifications are contemplated and considered equivalent.[0080]

While the invention has been described in conjunction with specific embodiments, it is evident that many alternatives, modifications, permutations and variations will become apparent to those of ordinary skill in the art in light of the foregoing description. Accordingly, it is intended that the present invention embrace all such alternatives, modifications and variations as fall within the scope of the appended claims.[0081]

Claims

What is claimed is:

1. A method of providing improved quality of service (QoS) control in an asynchronous network having a mediation device and a plurality of communication devices, comprising:

analyzing a plurality of quality of service (QoS) parameters relevant to a communication request received from a sender communication device of the plurality of communication devices to send a communication intended for a target communication device of the plurality of communication devices;

the mediation device making a determination on how to respond to the communication request based upon the analysis of the plurality of QoS parameters;

if the determination is that the communication request can be serviced, the mediation device servicing the communication request.

2. The method ofclaim 2, further comprising:

if the determination is that the communication request cannot be serviced, the mediation device sending a service message to the sender communication device of the plurality of communication devices.

3. The method ofclaim 1, further comprising:

the mediation device sending an acknowledgement to the sender communication device of the plurality of communication devices if the communication criteria can be satisfied.

4. The method ofclaim 1, wherein analyzing the plurality of QoS parameters further comprises:

analyzing a plurality of sender quality of service (SQoS) parameters of the plurality of QoS parameters relevant to communication criteria of the sender communication device.

5. The method ofclaim 4, wherein if the analysis of the plurality of SQoS parameters indicates that the communication criteria of the sender communication device can be satisfied, making the determination that the communication request can be serviced and servicing the communication request.

6. The method ofclaim 4, further comprising:

analyzing a plurality of target quality of service (TQoS) parameters of the plurality of QoS parameters relevant to the ability of the target communication device to receive the communication in accordance with the communication criteria.

7. The method ofclaim 6, wherein if the analysis of the plurality of SQoS parameters and the TQoS parameters indicates that the communication criteria of the sender communication device can be satisfied by the target communication device, making the determination that the communication request can be serviced and servicing the communication request.

8. The method ofclaim 6, further comprising:

analyzing a plurality of mediation device quality of service (MDQoS) parameters of the plurality of QoS parameters relevant to the ability of the mediation device to service the communication request.

9. The method ofclaim 8, wherein if the analysis of the plurality of SQoS parameters, the TQoS parameters and the MDQoS parameters indicates that the communication criteria of the sender communication device can be satisfied by the mediation device and the target communication device, making the determination that the communication request can be serviced and servicing the communication request.

10. The method ofclaim 8, further comprising:

analyzing a plurality of network quality of service (NQoS) parameters of the plurality of QoS parameters relevant to the ability of the network to service the communication request.

11. The method ofclaim 10, wherein if the analysis of the plurality of SQoS parameters, the TQoS parameters, the MDQoS parameters and the NQoS parameters indicates that the communication criteria of the sender communication device can be satisfied by the network, the target communication device, and the mediation device, making the determination that the communication request can be serviced and servicing the communication request.

12. The method ofclaim 6, further comprising:

13. The method ofclaim 12, wherein if the analysis of the plurality of SQoS parameters, the TQoS parameters and the NQoS parameters indicates that the communication criteria of the sender communication device can be satisfied by the network and the target communication device, making the determination that the communication request can be serviced and servicing the communication request.

14. An asynchronous communications network, comprising:

a plurality of communication devices;

a mediation device (MD) operable to provide improved quality of service (QoS) control in the asynchronous communications network;

wherein the mediation device analyzes a plurality of quality of service (QoS) parameters relevant to a communication request from a sender communication device of the plurality of communication devices to send a communication to a target communication device of the plurality of communication devices and makes a determination on how to respond to the communication request based upon the analysis of the plurality of QoS parameters.

15. The network ofclaim 14, wherein if the mediation device makes the determination that the communication request can be serviced, the mediation device services the communication request.

16. The network ofclaim 15, wherein prior to servicing the communication request the mediation device further sends an acknowledge message to at least one of the sender communication device and the target communication device that the mediation device will service the communication request.

17. The network ofclaim 14, wherein if the mediation device makes the determination that the communication request cannot be serviced, the mediation device sends a service message to the sender communication device.

18. The network ofclaim 14, wherein the mediation device analyzes a plurality of sender quality of service (SQoS) parameters of the plurality of QoS parameters that are relevant to communication criteria of the sender communication device.

19. The network ofclaim 18, wherein if the analysis of the plurality of SQoS parameters indicates that the communication criteria of the sender communication device can be satisfied, the mediation device determines that the communication request can be serviced and services the communication request.

20. The network ofclaim 14, wherein the mediation device analyzes a plurality of target quality of service (TQoS) parameters of the plurality of QoS parameters relevant to the ability of the target communication device to receive the communication in accordance with the communication criteria.

21. The network ofclaim 20, wherein if the analysis of the plurality of SQoS parameters and the TQoS parameters indicates that the communication criteria of the sender communication device can be satisfied by the target communication device, the mediation device determines that the communication request can be serviced and services the communication request.

22. The network ofclaim 20, wherein the mediation device analyzes a plurality of mediation device quality of service (MDQoS) parameters of the plurality of QoS parameters relevant to the ability of the mediation device to service the communication request.

23. The network ofclaim 22, wherein if the analysis of the plurality of SQoS parameters, the TQoS parameters and the MDQoS parameters indicates that the communication criteria of the sender communication device can be satisfied by the mediation device and the target communication device, the mediation device determines that the communication request can be serviced and services the communication request.

24. The network ofclaim 22, wherein the mediation device analyzes a plurality of quality of service (NQoS) parameters of the plurality of QoS parameters relevant to the ability of the network to service the communication request.

25. The network ofclaim 24, wherein if the analysis of the plurality of SQoS parameters, the TQoS parameters, the MDQoS parameters and the NQoS parameters indicates that the communication criteria of the sender communication device can be satisfied by the network, the target communication device, and the mediation device, the mediation device determines that the communication request can be serviced and services the communication request.

26. The network ofclaim 20, wherein the mediation device analyzes a plurality of network quality of service (NQoS) parameters of the plurality of QoS parameters relevant to the ability of the network to service the communication request.

27. The network ofclaim 26, wherein if the analysis of the plurality of SQoS parameters, the TQoS parameters and the NQoS parameters indicates that the communication criteria of the sender communication device can be satisfied by the network and the target communication device, the mediation device determines that the communication request can be serviced and services the communication request.

28. A mediation communication device of a plurality of communication devices operable to provide improved quality of service (QoS) control in the asynchronous communications network, comprising:

a processing and control element operable to analyze a plurality of quality of service (QoS) parameters relevant to a communication request from a sender communication device of the plurality of communication devices to send a communication to a target communication device of the plurality of communication devices and make a determination on how to respond to the communication request based upon the analysis of the plurality of QoS parameters.

a receiver, coupled to and controlled by the processing and control element, that receives the communication request from the sender communication device; and

a transmitter, coupled to and controlled by the processing and control element.

29. The device ofclaim 28, wherein if the processing and control element makes the determination that the communication request can be serviced, the processing and control element causing the transmitter to transmit the communication to the target communication device.

30. The device ofclaim 29, wherein prior to servicing the communication request the processing and control element causes the transmitter to send an acknowledge message to at least one of the sender communication device and the target communication device that the mediation communication device will service the communication request.

31. The device ofclaim 28, wherein if the processing and control element makes the determination that the communication request cannot be serviced, the processing and control element causes the transmitter to send a service message to the sender communication device.

32. The device ofclaim 28, wherein the processing and control element analyzes a plurality of sender quality of service (SQoS) parameters of the plurality of QoS parameters that are relevant to communication criteria of the sender communication device.

33. The device ofclaim 32, wherein if the analysis of the plurality of SQoS parameters indicates that the communication criteria of the sender communication device can be satisfied, the processing and control element determines that the communication request can be serviced and causes the transmitter to transmit the communication to the target communication device.

34. The device ofclaim 28, wherein the processing and control element analyzes a plurality of target quality of service (TQoS) parameters of the plurality of QoS parameters relevant to the ability of the target communication device to receive the communication in accordance with the communication criteria.

35. The device ofclaim 34, wherein if the analysis of the plurality of SQoS parameters and the TQoS parameters indicates that the communication criteria of the sender communication device can be satisfied by the target communication device, the processing and control element determines that the communication request can be serviced and causes the transmitter to transit the communication to the target communication device.

36. The device ofclaim 34, wherein the processing and control element analyzes a plurality of mediation device quality of service (MDQoS) parameters of the plurality of QoS parameters relevant to the ability of the mediation device to service the communication request.

37. The device ofclaim 36, wherein if the analysis of the plurality of SQoS parameters, the TQoS parameters and the MDQoS parameters indicates that the communication criteria of the sender communication device can be satisfied by the mediation device and the target communication device, the processing and control element determines that the communication request can be serviced and causes the transmitter to transmit the communication to the target communication device.

38. The device ofclaim 36, wherein the processing and control element analyzes a plurality of quality of service (NQoS) parameters of the plurality of QoS parameters relevant to the ability of the network to service the communication request.

39. The device ofclaim 38, wherein if the analysis of the plurality of SQoS parameters, the TQoS parameters, the MDQoS parameters and the NQoS parameters indicates that the communication criteria of the sender communication device can be satisfied by the network, the target communication device, and the mediation device, the processing and control element determines that the communication request can be serviced and causes the transmitter to transmit the communication to the target communication device.

40. The device ofclaim 34, wherein the processing and control element analyzes a plurality of network quality of service (NQoS) parameters of the plurality of QoS parameters relevant to the ability of the network to service the communication request.

41. The device ofclaim 28, wherein if the analysis of the plurality of SQoS parameters, the TQoS parameters and the NQoS parameters indicates that the communication criteria of the sender communication device can be satisfied by the network and the target communication device, the processing and control element determines that the communication request can be serviced and causes the transmitter to transmit the communication to the target communication device.

42. Computer-readable media tangibly embodying a program of instructions executable by a computer to perform a method to provide improved quality of service (QoS) control in an asynchronous network having a mediation device and a plurality of communication devices, the method comprising: